Thursday, December 28, 2006

The Year in Energy

Biowaste to fuels, cars that plug in, lithium-ion batteries that don't explode, and cheap energy from the sun.

By Kevin Bullis

Colonies of recombinant Streptomyces bacteria are designed to produce enzymes called cellulases. With these enzymes, the bacteria can break down cellulose on the way to producing ethanol. Credit: NREL/U.S. Dept. of Energy/Photo Researchers

Biowaste to ethanol could soon power cars.
Converting a vehicle to run primarily on ethanol costs just a couple of hundred dollars. But ethanol won't make much of a dent in gas use as long as the source of ethanol in the United States remains corn grain, which requires a lot of energy and land in order to grow. A much better alternative is cellulosic materials such as wood chips and switchgrass, which are both cheap to grow and require fewer natural resources. (See "Biomass: Hope and Hype.") In an effort to reduce the processing costs of these materials, researchers are genetically engineering organisms that can devour grasses and waste biomass, digest the complex sugars, and then transform the resulting simple sugars into alcohol. (See "Better Biofuels" and "Redesigning Life to Make Ethanol.") Already, advances in parts of this process have led to planned cellulosic-ethanol plants. (See "Making Ethanol from Wood Chips.")

The plug-in hybrid-vehicle era begins.
For years, hobbyists and a few companies have been adding bigger battery packs to hybrid vehicles, which have both battery power and an internal combustion engine, and plugging them into electrical outlets. This allows the cars, which typically rely on the electric power only for short bursts or to assist the onboard gasoline engine, to run on electricity alone for short trips. The idea of the "plug-in hybrid" has now caught the attention of government officials and researchers, who note that gas consumption would plummet if drivers could rely almost exclusively on electricity for average daily driving of about 33 miles. The gasoline engine would be available to boost performance and make it possible to use the car for long trips. Now the major car companies are taking notice and are finally developing plug-in hybrids. (See "GM's Plug-In Hybrid.") Meanwhile, researchers are beginning to anticipate benefits from plug-ins beyond gasoline conservation: millions of plug-in vehicles could serve as massive energy storage to stabilize the electric grid and make renewable energy sources more feasible. (See "How Plug-In Hybrids Will Save the Grid.") Battery costs still need to drop before such cars will approach the price of conventional hybrids or gas-only vehicles. But better batteries are already becoming available.

Massive recalls spark interest in better batteries.
The safety-related recall of millions of lithium-ion laptop and cell-phone batteries made by Sony and Sharp put batteries in the spotlight this year. Just in time, a new type of lithium-ion battery that uses materials inherently much safer than those involved in the battery recall started appearing in professional power tools. In addition to being safer, the new batteries are more powerful, have longer useful lifetimes, and are potentially less expensive than those utilized in laptops and cell phones today. All of this could make them attractive for use in mass-produced plug-in hybrids. (See "More Powerful Hybrid Batteries.") Meanwhile, a number of materials-science advances promise to as much as double the storage capacity of batteries and make them more long-lived. (See "3M's Higher-Capacity Lithium-Ion Batteries" and "Making Electric Vehicles Practical.")